Dry break couplers and mating adapters are commonly used to provide for quick coupling and decoupling of fluid conduits with no or minimal fluid spillage. A common dry break coupler includes a valve body and a locking sleeve. The locking sleeve is telescoped over the valve body and is movable axially between disengaged and engaged positions. When the locking sleeve is in its disengaged position, latching dogs in the valve body are free to move radially to permit mating of the valve body with an adapter. The locking sleeve then can be moved forwardly to its engaged position to hold the latching dogs in latched engagement with the adapter to prevent separation of the dry break coupler and adapter. With the coupler thusly coupled to the adapter, a lever on the valve body can be rotated to open a poppet valve in the valve body to establish fluid communication between flow passages in the coupler and adapter. When the lever is thusly rotated, a cam surface on the lever moves to a position blocking rearward movement of the locking sleeve out of its engaged position thereby to prevent decoupling of the coupler and adapter when the poppet valve is open.
In the petroleum transport industry dry break couplers have been used on the ends of loading arms for coupling to bottom loading adapters on rolling stock such as tank trucks. In the case of a truck terminal where petroleum product is loaded into tank trucks, an operator would typically manually maneuver the dry break coupler into alignment with the adapter at the bottom of the truck and then push the coupler into mating engagement with the adapter. Once mated, the locking sleeve is pushed from its disengaged to its engaged position To facilitate pushing of the locking sleeve, a common dry break coupler is provided with a pair of handles at diametrically opposite sides of the locking sleeve. An operator may grip these handles and push preferably with equal force against the handles to push the sleeve to its engaged position without cocking of sleeve.
Problems arise when an operator attempts to push the locking sleeve to its engaged position when the dry break coupler is not properly aligned with and mated with the adapter. If the coupler axis is skewed to the axis of the adapter, or if the coupler is otherwise not fully mated with the adapter, interference between the latching dogs and a latching flange on the adapter can prevent free movement of the locking sleeve from its disengaged position to its engaged position. When this occurs, an operator may then attempt to force the locking sleeve into its engaged position while continuing to attempt to move the coupler into proper alignment with the adapter. This is difficult to accomplish using the handles on the sleeve because of their location and lack of any leverage. Instead, operators have in the past grasped and rotated the poppet valve lever to use the cam surface on the lever to forcibly drive the sleeve to its engaged position. This results in increased wear and breakage of coupler components, particularly at the surface of locking sleeve against which the lever cam surface bears. When such wear has progressed to a point that the cam surface no longer will function to prevent retraction of the locking sleeve when the poppet valve is open, the locking sleeve must be repaired or replaced. Another part that is subject to premature failure is a pin that is typically used to connect the poppet valve lever to a shaft journalled in the valve body. Excessive forces applied to the lever during such camming of the locking sleeve to its engaged position cause the pin to break or bend.